The characteristics of water environmental geochemistry in east Dongting Lake, China

摘要

East Dongting lake was studied in order to gain the knowledge of water environmental geochemistry. The vertical water profile in the lake was sampled on 3 different locations from Dec, 2004 to July, 2005. Water samples were analyzed for total concentrations of N, P, Cu, Pb, Zn, Cr, Cd, As, Hg, K~+, Na~+, Ca~(2+), Mg~(2+), HCO_3~-, NO~_3~-, Cl~- and SO_4~(2-). Temperature, concentration of dissolved O_2 (DO), pH and transparency were measured in situ. Water quality data in the East Dongting lake from Jan., 2002 to May, 2004, provided by environment protection station of Dongting Lake, were also comprised in this paper. The results showed that: the transparency value was less than 1m, pH value was range from 6.74 to 8.54; DO content in the lake range from 5.25mg/L to 13.70mg/L; average total ionic amounts was 193 mg/ L ; average content of TN was 1.21 mg/ L ; contents of TP was 0.13 mg/ L ; N/ P ratio was 9.9:1, it can be concluded that phosphorus was the major nutrient element limiting biological productivity in the lake. The contents of heavy metals (Cr, Ni, Fe, Cd, Pb, Hg and As) in the lake showed that heavy metals were not the key factor controlling water quality in East Dongting lake. Most environmental geochemistry parameter in East Dongting lake changed according to the water-level of the lake, which was consistent with the character of Dongting lake as an open channel for Yangtze River.